The present invention relates to a display apparatus such as a plasma display apparatus. More particularly, the present invention relates to a configuration of a circuit for driving a display unit.
A variety of conventional display apparatuses are known. One of them is a plasma display apparatus. A plasma display apparatus reproduces an image by driving a fluorescent material to emit light in an electrical discharge phenomenon. In a plasma display apparatus, a large screen can be implemented in a small space. Thus, the plasma display apparatus is a future display apparatus which draws attention.
FIG. 2 is a block diagram showing a typical configuration of the conventional plasma display apparatus. In the figure, reference numerals 3 and 8 denote a plasma display panel and a first-electrode drive circuit respectively. Reference numeral 27 denotes a drive circuit whereas reference numerals 25 and 26 each denote a power MOSFET. A symbol X denotes a first electrode or an X electrode common to the power MOSFETs 25 and 26. A sustain power supply is connected to a terminal 7. Reference numeral 10 denotes an address drive circuit. Symbols A1 to AN each denote an address electrode. Reference numerals 82 and 33 denote a second-electrode sustain circuit and a drive circuit respectively. Reference numerals 31 and 32 each denote a power MOSFET whereas symbols Y1 to Yn each denote a second electrode. A sustain power supply of the second electrodes Y1 to Yn is connected to a terminal 29. Reference numeral 34 denotes a scan drive circuit which comprises first to nth sustain drive circuits 34a to 34n. The outputs of the first to nth sustain drive circuits 34a to 34n are connected to the second electrodes Y1 to Yn. The scan drive circuit 34 comprises a shift register 36, logic circuits 35 and 37, constant-current power supplies 39 and 47, power MOSFETs 38, 40, 42, 43, 46, 48, 50 and 51, resistors 41 and 49 as well as diodes 44, 45, 52, 53 and 80. A scan power supply is connected to a terminal 28, furnishing power to the scan drive circuit 34 by way of a diode 80. Reference numeral 11 denotes a waveform control circuit for outputting control signals Dxs, Dad and Dys to a first-electrode drive circuit 8, an address drive circuit 10 and a second-electrode sustain circuit 82 respectively. The waveform control circuit 11 also supplies a control signal Dscn to the scan drive circuit 34 by way of an insulation circuit 30. A second drive circuit 81 comprises the second-electrode sustain circuit 82 and the scan drive circuit 34.
In the plasma display apparatus shown in FIG. 2, the scan signal Dscn output by the waveform control circuit 11 is supplied to the shift register 36 employed in the scan drive circuit 34n by way of the photo-coupler insulation circuit 30. The shift register 36 sequentially distributes the scan signal Dscn to the scan drive circuits 34a to 34n. In the scan drive circuit 34, scan pulses bases on the scan signal Dscn are sequentially supplied to the second electrodes Y1 to Yn of the plasma display panel 3.
The second-electrode sustain circuit 82 generates sustain pulses YS based on the sustain pulses Dys output by the waveform control circuit 11. The sustain pulses YS are supplied to the second electrodes Y1 to Yn of the plasma display panel 3. The sustain pulses YS generated by the second-electrode sustain circuit 82 are also supplied to the second electrodes Y1 to Yn by way of a common terminal 83 of the scan drive circuit 34, the diode 45 and the diode 53.
The address signal Dad generated by the waveform control circuit 11 is supplied to an address drive circuit 10. The address drive circuit 10 outputs address drive pulses based on the address signal Dad to the address electrodes A1 to An of the plasma display panel 3.
The first-electrode drive signal DXS generated by the waveform control circuit 11 is supplied to a first-electrode drive circuit 8. The first-electrode drive circuit 8 outputs drive pulses based on the first-electrode drive signal DXS to the first electrode X of the plasma display panel 3. The scan drive circuit 34 is available in the market as a scan drive IC.
A conventional implementation of the plasma display apparatus shown in FIG. 2 is disclosed in U.S. Pat. No. 5,745,086. FIG. 10 of this U.S. patent is a block diagram showing a basic circuit for driving the plasma display apparatus.
In the plasma display apparatus shown in FIG. 2, the scan drive circuit 34 composing the second-electrode drive circuit and the second-electrode sustain circuit 82 employ circuits independent of each other. For example, the second-electrode drive circuit 34 has a configuration employing a scan drive IC having a circuit configuration shown in FIG. 2 while the second-electrode sustain circuit 82 has a configuration employing a power module. In addition, since the terminal 83 of the second-electrode sustain circuit 82 is floating off the ground, it is necessary to put the scan signal Dscn in a floating state through the insulation circuit 30.
Moreover, the circuit scale of the second-electrode drive circuit 34 is larger than the first-electrode drive circuit 8, resulting a big ratio of the second-electrode drive circuit 34 to the entire circuit of the plasma display apparatus. Accordingly, the second-electrode drive circuit 34 is a problem encountered in an effort made to reduce the size of the plasma display apparatus.